This invention relates generally to stationary structures in gas turbine engines, and more particularly to support frames in such engines.
A typical turbofan engine includes in serial flow communication a fan, a low pressure compressor or “booster”, a high pressure compressor (“HPC”), a combustor, a high pressure turbine (“HPT”), and a low pressure turbine (“LPT”), with the HPT driving the HPC, and the LPT driving both the fan and the booster.
The rotating components of a gas turbine engine are supported by bearings mounted in one or more structural frames. The frames typically take the form of an inner hub connected to an outer casing by an array of radially extending airfoil-shaped struts. Typical turbofan engines have a fan hub frame (“FHF”) just aft of the fan.
Conventional turbofan engines often incorporate a variable bleed valve (“VBV”) system for controlling booster compressor stall margin. The VBV system includes one or more bleed valves mounted within the fan hub frame. The valves are open during low power operation of the engine, such as at idle, for bleeding a portion of the compressed air. The bleed valves are closed at high power operation of the engine, such as during cruise or takeoff, since bleeding is no longer required. When the valves are open, air is passed from the booster flowpath through the fan hub frame and into a bypass duct.
In prior art turbofan engines the fan hub frame area includes, in addition to the fan hub frame itself, numerous attached components such as separate VBV ducts to direct the bypass flow, fire-resistant fire blankets to protect the fan hub frame, and cowl supports. While effective, these structures increase the weight, complexity, and cost of the engine.
Accordingly, there remains a need for a ducted cowl support which provides structural support and a fluid bypass flowpath.